1. Field
Example embodiments relate to a capacitor, and for example, to a capacitor that is formed by a conductive line and/or has high electrostatic capacity, an integrated circuit having the capacitor, and/or a method of fabricating the capacitor.
2. Description of Related Art
Capacitors may be formed in integrated circuits for various purposes. For example, a plurality of capacitors may be included in memory devices, for example random access memory (RAM), analogue devices, for example a radio frequency (RF) device or a mixed signal device, and/or large scale integrated circuits. In general, a capacitor may be configured to store as much charge as possible because charge may be lost due to leakage or other reasons. For example, as the overall size of semiconductor devices decreases, a technique that realizes a higher charge capacity in a smaller space may be desirable.
If an integrated circuit including capacitors is manufactured, the area of the integrated circuit may be reduced if the electrostatic capacity per unit area is increased, and accordingly, integration density of the integrated circuit may be increased. Various configurations of capacitors may be used in an integrated circuit, for example, a metal-insulator-metal (MIM) capacitor having a structure including a dielectric layer disposed between a pair of flat electrodes may accumulate charge using electrostatic induction between the electrodes. Accordingly, the electrostatic capacity C of the capacitor may be calculated according to the following Equation (1).C=εrε0S/d  (1)where εr is the relative dielectric constant, ε0 is vacuum permittivity, S is the facing area of the capacitor electrodes, and d is the distance between the electrodes.
Recently, due to the development of miniaturization techniques for semiconductors, a larger number of wires may be formed per unit area by reducing gaps between the wires and/or multiple layers of wires may be stacked. Accordingly, wires in an integrated circuit may be arranged as parallel multiple layers in a surface direction or a vertical direction to have a maximum facing area per unit area. A capacitor having one or more of the various structures as described above may be a useful capacitor to increase electrostatic capacity while reducing the area of the integrated circuit according to the development of multi-layer techniques in the future.
A vertical parallel plate (VPP) capacitor may be an example of a capacitor formed in an integrated circuit. FIG. 1 is a plan view of a conventional VPP capacitor structure, and FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1.
Referring to FIGS. 1 and 2, the conventional VPP capacitor may include a first pad 14 and a second pad 24 facing each other and respectively connected to an external power source (not shown), a first electrode stem 12 and a second electrode stem 22 respectively connected to the first pad 14 and the second pad 24, and a dielectric 30 between the first electrode stem 12 and the second electrode stem 22. For example, the first electrode stem 12 and the second electrode stem 22 maintain a constant distance, and a plurality of first electrode branches 10 and second electrode branches 20 respectively extend from the first electrode stem 12 and the second electrode stem 22 toward opposite electrodes. The adjacent first electrode branches 10 and second electrode branches 20 are formed in an interlock shape. Namely, the first electrode stem 12 with the first electrode branches 10 interdigitate with the second electrode stem 22 with the second electrode branches 20.
The electrostatic capacity of the conventional VPP capacitor may be calculated by Equation 1 by using the areas of the electrode branches, the distance between the electrodes, and the dielectric constants of the dielectrics. Accordingly, measures to increase the electrostatic capacity of the capacitor may include using a dielectric having a higher dielectric constant, reducing the thickness of the dielectric, or increasing an area that the electrodes oppose each other by increasing the number of electrode branches. However, the reduction of the thickness of the dielectric may increase the current leakage and/or increasing the number of the electrode branches may increase the overall size of the integrated circuit, thereby limiting the increase of the electrostatic capacity. For example, if a dielectric having a higher dielectric constant such as an inter-metal dielectric (IMD) or an inter-layer dielectric (ILD) is used, there is a higher possibility of increasing the RC delay time constant.